Reducing one third the dose of porcine follicle-stimulating hormone did not affect the in vivo embryo production in Santa Inês ewes

Context Superovulation is still a main limitation of multiple ovulation and embryo transfer programs because of its high cost and the variability in the responses to the hormonal protocols used. Aims This study aimed to compare the effect of two doses of porcine follicle-stimulating hormone (pFSH) on follicular growth, superovulatory response, and in vivo embryo production of Santa Inês ewes. Methods A total of 40 multiparous ewes received a Day 0 estrus synchronization protocol and were superovulated with either 333 IU (G333, n = 20) or 500 IU (G500, n = 20) of pFSH. Ultrasonographic evaluations of ovaries were performed every 12 h, from the first pFSH dose until 60 h after the last dose. Ewes were naturally mated and submitted to non-surgical embryo recovery. A subsample of viable blastocysts (G333: n = 10; G500: n = 8) was stained with Nile Red to quantify lipid droplets. Key results The number of small, medium, and large follicles, and the size of the largest follicle, varied over time (P < 0.0001), even though there was no difference between the treatments. The pFSH dose also did not affect estrous behavior rate (95% vs 100%), superovulatory response (75% vs 70%), recovery rate (52.4% vs 56.4%), viability rate (73.8% vs 62.3%), recovered structures (5.9 vs 5.3), viable embryos (4.9 vs 3.7), and lipid accumulation in embryos (132.9 vs 129.4 arbitrary fluorescence units), for G333 and G500 respectively. Four ewes (10%) had premature luteal regression. It should be noted that all viable embryos recovered were Grade 1 or 2, that is, freezable embryos. Conclusions In conclusion, 333 IU of pFSH is enough to reach a similar superovulatory response as obtained from 500 IU of pFSH in Santa Inês ewes. Implications The use of lower doses of pFSH could reduce costs per embryo produced.